The present invention relates to a solid state image sensor comprising pixels each of which includes a lateral type static induction transistor, and more particularly to a solid state image sensor having an electronic shutter function.
In a video camera comprising a solid state image scnsor, since a light signal storing period corresponding to a shutter open period (shutter speed) is fixed to a constant period such as 1/60 second or 1/30 second in NTSC system, it is impossible to adjust freely the depth of field in accordance with the intension of a user. Moreover, since the shutter speed is fixed, when an object moving at a high speed is picked-up and recorded and then the recorded image is reproduced in a still mode, it is impossible to reproduce a sharp image.
The above mentioned drawbacks of the known solid state image sensor are mainly due to the fact that the shutter speed is fixed. In another known video camera using an interlace-line-transfer CCD image sensor (IL-CCD) or a frame-transfer type CCD (FT-CCD), the shutter speed may be variable, because image pick-up elements have the shutter function. However, due to the inherent characteristics of CCD, an amount of charge carriers which cause an output image signal is small, and thus the sensitivity is relatively low and S/N of the image signal is also small.
It has been also proposed to arrange a mechanical shutter in the video camera comprising the solid state image sensor. However, the mechanical shutter mechanism is complicated in construction and large in size and further life time, accuracy and reliability of the mechanical shutter are also insufficient. Further, it is undesired to use the mechanical shutter in view of the recent tendency of the compact video camera.